The present invention relates generally to surgical fastening tools for fixating tissue and/or surgical materials during minimally invasive surgery, and particularly to a surgical fastening tool having a space-efficient, simplified fastening mechanism that permits deployment of the tool through a minimal opening but which also maximizes the gripping area of the applied surgical fastener. More particularly, the invention relates to a reduced diameter (5 mm) surgical fastening tool for use in hernia repair. The tool is deployed through a reduced diameter access port in the body to fasten a piece of surgical mesh to body tissue using a specially formed fastener having a maximized gripping area. The tool also has a simplified, jam-free fastening mechanism. The present invention also relates to methods for repairing a patient""s hernia through a minimized diameter access port while maximizing the gripping area of the surgical fastener as well as methods for applying surgical fasteners from a miniatured device with reduced risk of jamming.
During some surgical procedures, most notably hernia repair procedures, it is considered desirable by many practitioners to reinforce the muscle tear or other defect with a piece of surgically implantable mesh. Physicians most often use an open-weave, sintered mesh made of polypropylene and hold it in place by a type of permanent fixation method. One common method of fixation uses metallic fasteners, such as staples, which remain in the body permanently after the hernia repair. Medical device designers have created a number of larger-size devices to fasten tissue and/or surgical materials to tissue during minimally invasive surgery. According to these designs, the devices typically contemplate a 10-mm or wider application tool used to deploy a fastener. For example, Green et al., U.S. Pat. No. 5,356,064, col. 21, 11. 34-53, describes a device for deployment through a 12 mm trocar guide tube wherein the device stacks a set of staples at roughly a forty-five degree angle to the axis of the device to provide greater visibility. See Green et al. FIG. 18.
However, these tools are being judged too large for deployment according to the current minimally invasive techniques which are bringing the size of the surgical instruments and access ports down to a 5 mm diameter. Moreover, Green et al. cannot be readily scaled down because of physical limitations caused by the generally transverse stacking of fasteners. See Green et al., FIG. 18. In addition, the design of Green et al. cannot be effectively scaled down because the fastener discharged by the application tool must be of sufficient scale to securely span across the defect and/or strands of surgical mesh and efficaciously engage sufficient tissue area for adequate gripping strength. Green et al. employs a fastener forming system which unduly reduces the finished span or width of the fastener relative to its initial width. See Green et al., FIGS. 20-21, col. 22, 11. 38-48. Thus, reduction in Green et al.""s tool diameter would result in an unsatisfactory gripping area for the finished fastener.
In addition to reducing fastener-gripping strength, smaller diameter tools have other problems. For example, miniaturization of the surgical fastening tool increases the likelihood of jamming, a common problem for minimally invasive surgical fastener tools, because the critical tolerances for the device""s moving parts would be reduced along with the size of the instrument. Accordingly, slight changes in deployment stress and temperature can effect the mobility of the moving tool parts. The Origin Tacker, though of 5 mm diameter, employs a rotational actuation mechanism to deploy a helical fastener. Rotation increases the complexity needed for the actuation mechanism, and creates greater need to ensure reliable translation of trigger action.
What is needed is a space-efficient surgical fastening tool that minimizes its outer diameter while maximizing the gripping area and strength of the fastener. The fastening mechanism of the desired surgical fastening tool must not be complicated and should be limited to a few actuated parts to reduce the probability of jamming during minimally invasive surgery. The device should be designed to avoid double firing and incomplete firing. The device should also permit for the easy reloading of additional fasteners during extensive surgical procedures. The prior art devices are inadequate to meet these objectives.
The present invention relates to surgical fasteners, fastening tools and methods for securing tissue and/or surgical materials during minimally invasive surgery. In particular, the devices of the present invention are adapted to minimize the diameter of the surgical fastening tool while maximizing the area gripped by the fastener. Furthermore, the devices of the present invention are adapted to discharge the fastener by way of a simplified fastening mechanism with few actuated parts. The surgical materials to be fastened may be surgical mesh, sutures, prostheses, linings or the like. The tissue to be fastened may be tissue, foreign or endogenous to the patient.
In one embodiment, the apparatus includes three major elements: a fastener applicator comprising a fastener magazine; a handle portion to which the applicator is attached; and a triggering mechanism. The triggering mechanism may be housed in either the fastener applicator, the handle portion or in a combination of the two. In a first aspect of the invention, the fastener applicator has a cantilevered anvil with a cross section around which the fastener may be formed at a single focal point when the fastener is pressed by a slide. The fastener may initially be M-shaped, upside-down U-shaped or other suitable shape. In a most preferred embodiment, the anvil has a cross section that is essentially triangular and a shaping slide with a cooperating notch that is angled to closely receive the triangular cross-section of the anvil. FIG. 1. Importantly, according to this first aspect of the invention, the single-point anvil permits the width of the slide which forms the fastener to be the same or less than the width of the stored fastener but without sacrificing the finished span (installed width) of the applied fastener and the area it encloses. An anvil with a semi-circular or other round edged cross-section may also be used in combination with a round-notched slide. The space-efficiency of the slide and anvil permits a reduction in the overall width of the fastener applicator relative to the width of the fastener. Traditional staple type surgical fasteners have a slide which, when of reduced width, unacceptably reduce the span of the applied fastener to accommodate the xe2x80x9chornsxe2x80x9d of the slide. See FIG. 2.
In one embodiment, the apparatus is of unitary, non-detachable design wherein a fastener applicator, handle portion and a triggering mechanism are provided in a single integral unit. The fasteners may be stored in the handle portion of the apparatus or loaded from outside the device just prior to use. However, according to a second aspect of the invention, the applicator functions as a fastener magazine and is readily removed from or locked onto the handle portion by virtue of a novel mechanism for quick attachment and detachment. The applicator comprises a slide actuator which operates a slide in response to operation of the triggering mechanism to discharge fasteners. The novel mechanism locks the slide actuator into a secure, locked position within the detached applicator magazine so that the slide actuator is properly located to engage the motion-translating parts of the triggering mechanism of the device when attached. The novel mechanism then automatically frees the slide actuator upon attachment of the applicator to the handle thereby making the device ready for use. Specifically, the novel mechanism employs an xe2x80x9cL-shapedxe2x80x9d pin with a recessed region that rotates into and out of engagement with the slide actuator based on its interaction with pre-formed recesses in the handle of the device during attachment and detachment. Thus, according to a preferred embodiment employing this second aspect, when the applicator comprising a magazine of fasteners runs out of fasteners, the user may substitute a second applicator containing a fresh magazine. This construction also permits the handle portion to be sterilized and re-used.
The fastener applicator may either be of unitary construction or made of several interconnecting pieces. However, in the preferred embodiment, a tube of circular cross-section houses a magazine formed by the juxtaposition of two cooperating half shells, known collectively as the insert, each half-shell having essentially a semi-circular cross section. The two-half shells are preferably inserted into the tube during manufacture. When combined, the two half-shells and the slide form the magazine or storage channel which contains a set of vertically stacked fasteners. The fastener applicator is separable from the handle portion so that the handle portion may be supplied with a new applicator containing a new set of fasteners once the first set of fasteners has been used.
A third aspect of the invention minimizes the possibility of jamming caused by an improperly timed interplay between independently moving parts and also reduces the probability of jamming due to the failure of the trigger to actuate a key part of a multi-part actuation mechanism. Thus, in the preferred embodiment of the device employing the third aspect of the invention, the insert and slide form two channels: a fastener storage channel and a fastener-driving channel. The fastener storage channel contains a plurality of vertically stacked fasteners, stacked tips to back, thereby reducing applicator width relative to tools which use transversely stacked fasteners. The fasteners are continually urged toward the distal end of the applicator by a pusher that is biased by a pusher spring. The fastener-driving channel further houses a slide that rides in the driving channel to engage the back of the first fastener positioned within the driving channel. According to the most preferred embodiment, movement of the slide drives the fastener onto the anvil while the notch in the slide shapes the fastener over the anvil according to the first aspect of the invention.
In the preferred embodiment, the insert additionally comprises a system of leaf springs that assist in securely positioning and advancing the fasteners one at a time during the repeated fastener application process. The action of the leaf springs is controlled by slide location. Accordingly, in the most preferred embodiment of the third aspect, the applicator contains one actuated part, the slide, that is moved by the active application of force generated by the triggering mechanism. The rest of the moving parts in the applicator are biased to move in a certain direction but are restrained or liberated based on the location of the slide.
According to this most preferred embodiment, with the applicator held against the target, the slide is fully advanced distally to drive the first fastener""s tips into the target and to shape the fastener on the anvil. When the slide is subsequently retracted after shaping the first fastener, a pair of biased ejector springs are liberated and kick the formed fastener off the end of the anvil, freeing the apparatus from the fastener. Upon further retraction of the slide, a biased fastener positioning spring is released and pushes the second fastener from the distal most position in the storage channel into the driving channel. Meanwhile, a biased stop spring restrains the third fastener from advancing in the storage channel until the second fastener is being advanced in the driving channel. The third fastener is then released by the depressed stop spring and advanced to the distal most position in the storage channel. Fully actuating the slide to discharge the second fastener and then fully retracting the slide positions the third fastener in the driving channel. This process may be repeated until each of the fasteners in the magazine has been applied.
In the interest of further reducing the potential for jamming of the miniaturized tool during surgery, according to a fourth aspect of the invention, the apparatus may employ a unique jam-free ratchet and pawl mechanism, housed in the handle portion, that assures complete travel of the slide in both directions during application of each fastener. This embodiment of the apparatus comprises a plunger assembly that is linked to the slide by means of the slide actuator. Complete forward and reverse movement of the plunger assembly results in a complete corresponding motion of the slide. In the preferred embodiment, the plunger assembly reciprocates forward and backward within the body of the handle portion. The body of the handle has a tapered slot, adjacent to the plunger assembly, which contains a pawl. The side of the plunger assembly that is immediately adjacent to the tapered slot contains a series of grooves which collectively form a ratchet extending for a distance approximately equal to the travel of the plunger assembly. The length of the pawl is longer than the perpendicular distance from the bottom of the tapered slot to the bottom of the ratchet grooves, such that once the pawl is engaged in the ratchet grooves, the pawl is oblique and prevents reversal of the plunger""s direction of travel.
When the pawl has moved past the end of the ratchet, a wire spring urges the pawl to assume a position transverse to the direction of travel. As the plunger assembly is moved back towards its original position, the pawl again engages the ratchet but with opposite orientation. Accordingly, the pawl again prevents reverse travel of the plunger assembly until the stroke is fully completed and the pawl has cleared the length of the ratchet. The spring then reorients the pawl transversely in preparation for the next stroke. In this way, the invention prevents the slide, which is connected to the plunger assembly by the slide actuator, from reversing mid-stroke and safeguards against jamming, non-firing and misfiring.
The methods of the present invention relate to deploying a fastener with maximized gripping area using a space-efficient deployment mechanism having few actuated parts. In a preferred method of the invention, a hernia repair patient is incised and fitted with a port to access the site of the hernia. After access to the site of the hernia is achieved, the hernia is reduced and the surgical mesh is placed over the defect using minimally invasive techniques. The surgical fastening tool apparatus is deployed through an access port and its tip pressed against the mesh and the tissue to be fastened. The tool is then triggered by means of the triggering mechanism. The fastener is then formed by the action of the slide pressing the fastener onto the surface of the anvil. In this manner, the mesh is secured to the body tissue by the gripping strength of the fastener.
When employing the first aspect of the invention, the method of the present invention generally includes the following steps: forming a fastener by placing it over a single focal point anvil; pressing the fastener against the single focal point anvil using a slide having a width that is approximately the same as or less than the width of the fastener; discharging the fastener into the tissue of the patient.
In a method that employs the second aspect of the invention, the method of fastener application is executed within a detachable applicator which may be readily replaced with a second applicator containing additional fasteners using a novel mechanism.
In a method that employs the third aspect of the invention, a fastener is applied by the following preferred steps: the fastener is moved from the storage channel where it has been vertically stacked to the driving channel by the biased fastener positioning spring as the slide is retracted; the slide is then advanced until the slide engages the fastener in the driving channel and drives the fastener over the anvil to form the fastener. During advancement of the slide the biased stop spring is forced back into a recess in the insert thereby allowing the next fastener to move forward in the storage channel in response to the force of the biased pusher spring; the slide is then retracted, freeing the biased ejector springs to kick the formed fastener off the end of the anvil; finally the slide is further retracted until the fastener positioning spring is once again is free to move the distal-most fastener from the storage channel into the driving channel.
The present invention was developed, in part, out of recognition of the need for a reduced diameter fastening tool which could discharge, from a reduced diameter applicator, a fastener that firmly holds mesh and tissue together. Unlike a traditional staple shape where the back of the staple lies parallel to the tissue surface into which it is deployed, the present invention teaches that a U-form wire fastener applied in the form of a diamond relative to the tissue surface has certain advantages including reduction in the size of fastener needed to achieve high gripping strength. The installed span of the fastener and the area captured by the fastener are two useful parameters for evaluating the efficacy of a fastener. FIGS. 3a and 3b on Table 1 demonstrate the conventional finishing of a xe2x80x9cUxe2x80x9d shaped staple by assuming an arbitrary initial width of 8 mm (assuming negligible thickness of the wire and bends of 90 degrees) and monitoring these two parameters. The traditional xe2x80x9cUxe2x80x9d-shaped staple may have many finished shapes depending on the width selected between bends in the back of the staple. In essence, the width between bends determines the finished span of the applied staple. See FIG. 3b. The length of the staple legs is arbitrary but the legs should not reach too deeply into the tissue to avoid damaging underlying structures. On the other hand, the staple must reach deeply enough to enclose sufficient tissue to develop adequate holding strength.
With reference to FIG. 3b and Table 1, it is clear that, as the finished conventional staple span is stepwise decreased, the area of the projected rectangle formed by the finished staple goes through a maximum value (8). By comparison, the invention""s preferred diamond shaped fastener, described in FIG. 4b and Table 2, has a finished span of 0.707xc3x97the initial width, W, and encloses a projected area double the size of the maximum traditional design (16). Moreover, the preferred diamond-shaped finished fastener shown in FIG. 4b, maintains a span greater than all but the most extreme of possible finished shapes made by the conventional process (shapes which suffer from greatly diminished gripping area). Although the user may choose other initial widths as well as other bend angles for the traditional method, the relative relationship between the gripping area of the diamond fastener of the present invention and the conventional finished fastener remain. When viewed in light of the longer finished span permitted by the present invention, these Figures and Tables demonstrate the superior geometry of the finished fastener formed by the instant apparatus.
      TABLE    ⁢          xe2x80x83        ⁢    2        FASTENER    ⁢          xe2x80x83        ⁢    FORMED    ⁢          xe2x80x83        ⁢    BY    ⁢          xe2x80x83        ⁢    PREFERRED    ⁢          xe2x80x83        ⁢    EMBODIMENT    ⁢          xe2x80x83        ⁢    OF              THE      ⁢              xe2x80x83            ⁢      INVENTION        ⁢          xe2x80x83                          (                  W          2                )                    (                  Span          2                )              =                  2            1            SPAN    =                            1                      2                          ⁢        W            =              0.707        ⁢        W                  AREA    =                  (                  w          2                )            2                                    Thus          ,                                    if              ⁢                              xe2x80x83                            ⁢              W                        =            8                    ,                                      SPAN          =          5.66                                              xe2x80x83                                      AREA          =          16                    
To the extent the finished angle of the inserted legs relative to the surface plane of the tissue is related to the fastener""s strength, a fastener""s legs which finish parallel to the tissue surface are superior to those which finish perpendicular to tissue. Accordingly, in an alternate embodiment, described in FIGS. 5a and 5b and Table 3, the fastener may be initially formed with an upwardly concave back of an arbitrary angle and with legs which are initially parallel, approximating the capital letter xe2x80x9cMxe2x80x9d. FIG. 5a. In the embodiment shown, the angle of the concave back is greater than ninety-degrees. During formation of the fastener the central bend is reversed to allow the legs to finish more parallel to the tissue surface. FIG. 5b. According to this embodiment, the length of the finished span remains essentially the same as the finished span shown in FIGS. 4a, 4b but the projected area gripped by the fastener is reduced.       TABLE    ⁢          xe2x80x83        ⁢    3        SPAN    ≥          .707      ⁢      W            AREA    =                            1          2                ⁢                              (                           greater than                               W                /                2                                      )                    2                    ≥      8      
The gripping area is reduced to a value that is still greater than or equal to the maximum area gripped by the conventionally processed U-shaped design described in FIG. 3b. Importantly, the finished span of the conventionally processed U-shaped design is substantially less (0.5 W=4) compared to the finished span of the concave back fastener (0.707 W=5.66). Thus, it is clear that with respect to the length of the finished span and the gripping area of the fastener, triangular finished fastener designs, shown in FIG. 5b, are also superior to conventionally processed designs. This recognition is particularly important when the goal is to miniaturize a surgical fastening tool for use in minimally invasive surgery.
Miniaturization of a fastener tool places a premium on the gripping efficiency of the fastener relative to the space available for its deployment within the small diameter of the applicator. Assuming that the applicator of a surgical fastening tool comprises a tubular housing, a slide that forms the U-shaped fastener with two bends in the back must have xe2x80x9chornsxe2x80x9d and be wider than the finished span thereby wasting tool diameter.
Thus, as a practical matter, the conventional mechanism necessarily results in a fastener with a smaller finished span for a given tool diameter. See FIG. 2. In contrast, the finished diamond and triangular fasteners shown in FIGS. 1, 4b and 5b, do not need the slide to be wider than the finished span of the fastener.
Using the fastener and anvil configurations of FIGS. 4 and 5, the tool design need not sacrifice the length of the finished span to accommodate the fastener forming apparatus itself. Moreover, the disclosed invention requires less force to deploy the fastener because only one bend is formed during deployment rather than two bends as with the conventional design. This reduction in force is a significant advantage for a miniaturized device whose miniaturized parts are relatively weak and may fail under repeated stress.
The present invention was also developed in part to solve other problems associated faith miniaturization of fastener devices, such as jamming, non-firing and misfiring. Thus, the invention contemplates that the deployment mechanism of the device has few mechanically actuated parts because the critical tolerances for such actuated parts are reduced in the miniaturization process. Moreover, surgical fastening tools are at times roughly handled in a hospital setting and may undergo significant abuse during sterilization. This can cause the internal uncoupling of actuated parts or other damage not visible from the surface of the tool, only to be discovered during use of the device. Thus, a feature limiting the number of actuated parts leads to a sturdier, more reliable device. This feature also simplifies the manufacturing process.
Finally, the invention was motivated by the knowledge that miniaturization of the surgical fastening tool may cause the tool to carry fewer fasteners than may be needed for a particular surgical procedure. Thus, according to another aspect of the invention, the fastening tool comprises an interchangeable fastener magazine.
If is a general object of the present invention to eliminate or reduce the problems associated with jamming of small diameter surgical fastening tools.
It is another object of the present invention to reduce the number of actuated parts in the deployment mechanism of the tool so as to reduce the number of critical tolerances between coupled parts and reduce the risk of decoupling or other malfunction. For example, in one embodiment of the invention, the insert of the fastener applicator incorporates only one actuated component.
Another object of the present invention is to maximize the gripping area of the fastener while reducing the diameter of the applicator of the surgical fastening tool. Because of the nature of surgical repair, it is undesirable to have to refasten the surgical material after surgery is completed. Accordingly, the fasteners should form a strong link between the fastened materials and/or tissue so that the materials stay in place during post-surgical patient activity. Secure fasteners have previously required larger diameter fastening tools which are incompatible with the new, reduced-diameter, minimally invasive surgery techniques.
It is a further object of the invention to provide a surgical fastening tool that is economical and convenient for fastening hernia mesh and the like during minimally invasive surgery.
It is a further object of the invention to provide a surgical fastening tool with an interchangeable magazine portion that permits fast and reliable introduction of new fasteners into the tool.
It is further object of the invention to provide a disposable, detachable applicator which contains a complete fastening mechanism and set of fasteners, thereby permitting both the fast, convenient replacement of fasteners during surgery as well as the reuse of the handle and trigger portions.
It is a further object of the invention to ensure complete travel of the tool""s fastening mechanism in each direction to prevent against partial firing, empty firing and jamming during use.
As for the methods of the invention, one object of the invention is to provide a fastening mechanism that is both compatible with minimally invasive surgery techniques using reduced port diameters (5 mm is the newest standard in the field of minimally invasive surgery) and which provides fasteners that maximally grip the area of tissue and material.
It is a further object of the invention to provide a method of applying a fastener during minimally invasive surgery that includes easy replacement of spent fastener magazines.
It is a further object of the invention to provide a reliable method for fastener application during minimally invasive surgery that avoids jamming, non-firing and misfiring.